Bowling pin with vibrating core



March 15, 1966 R. M. coNKLlN ETAL BOWLING PIN WITH VIBRATING CORE Filed March 27, 1963 INVENTORS:

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United States Patent O 3,240,494 BOWLING PIN WITH VIBRATING CORE Robert M. Conklin and John l. Weisz, Muskegon, and Anton W. Rytina, Grand Haven, Mich., assignors to Brunswick Corporation, a corporation of Delaware Filed Mar. 27, 1963, Ser. No. 268,304 3 Claims. (Cl. 273-82) This invention relates to bowling pins and adjustment of their sound characteristics.

Conventionally and in accordance with the specifications of the American Bowling Congress, regulation bowling pins are constructed essentially of a sound hard maple core. Such bowling pins often have plastic coatings covering the maple core. In addition, the weight range for regulation pins and a maximum variance in weight between pins of a given set are also prescribed for regulation pins. With dwindling supplies of suitable maple stock a'nd resulting increased cost of such stock, attention has been directed to other materials for use in replacing hard maple cores. Among such other core materials are other Woods, part plastics, metals and the like.

One difficulty encountered in the use of other than maple cores in bowling pins is that of maintaining good pin sound characteristics. An experienced bowler, who is used to the sound of a plastic-coated hard maple core pin when struck by a bowling ball will notice differences in sound due to other core materials. Because differences in sound can be caused by pin defects, bowlers may often refuse to play such pins believing the pin to be in some way defective.

It is a general object of this invention to provide for adjustment of resonance -fof bowling pins as set out herein and to further provide new and useful bowling pins having adjusted sound characteristics.

It is a further object to provide a new and useful bowling pin having a hard resonant core and a coating over the core wherein the stiffness or varea moment of inertia below the bowling pin neck is decreased for providing adjusted sound characteristics.

It is another object to provide such a bowling pin in accordance with the foregoing objects wherein a dampening coating material is used for the coating and especially wherein the coating material is disposed in a mass at the upper end or head of the bowling pin to add weight thereto for changing the natural frequency of vibration of the core and/or to exert a sound-dampening effect.

A still further Object of this invention is t0 provide a bowing pin in accordance with the foregoing objects wherein the hard bowling pin core is a hollow metal core and especially wherein the sound characteristics are adjusted to provide a predominant audible natural frequency in the range of the predominant audible natural frequency of a plastic-coated hard maple core pin.

Yet another object of this invention is to provide a new and useful method for adjusting the sound characteristics of a bowling pin, e.g., during manufacture of the bowling pin.

Further objects will become readily apparent from the following detailed description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a partiall vertical section through an embodiment of a bowling pin in accordance with this invention; and

FIGURE 2 is a Vertical section through a part of another bowling pin for comparison purposes.

While an illustrative embodiment of the invention is shown in the drawing and will be described in detail here- 1n, the invention is susceptible of embodiment in many different forms, and it should be understood that the present disclosure is to be considered as an exemplitication of the principles of the invention and is not intended to limit the scope to the embodiment illustrated.

Referring to the drawing, there is illustrated in FIG- URE l an embodiment of a bowling pin of this invention indicated generally by reference numeral 10 which includes a hollow metal core 14, which may, for example, be cast or otherwise formed from a metal or metal alloy such as steel, magnesium or aluminum or alloys of magnesium and/ or aluminum or the like. In accordance with Iconventional terminology, pin 10 and core 14 will referred to herein as having a head portion indicated generally by reference numeral 11, a neck portion indicated generally by reference numeral 12, and a shoulder portion indicated generally by reference numeral 13. Core 14 has a coating or cover 15 thereover and the coating 15 may be provided with a protective layer or coating 16 of a more tenacious composition, such as nitrocellulose lacquers or polyurethane lacquers, or other protective coating materials which will be evident to those in the art.

The coating 15 may be composed of any coating material or mixture of materials having sound dampening properties in their set or cured state. Thus, any of the usual pin coating materials can be used. More advantageously, the coating material may be suiliciently elastic to absorb shock and sufliciently resilient to maintain the outer shape of the bowling pin after repeated impacts. The coating material is usually softer and more elastic than the hard core and is preferably resistant to cold ow.

As a more specific example of a coating composition, coating 15 may be a cured resilient elastomeric composition including parts by weight of a resin marketed under the trade name Adiprene L-100, 9 parts by weight of castor oil and 3.2 parts by weight 1,4-butanediol. The Adiprene resin is a polyurethane-type resin and consists of a linear condensation polymer of 1,4-butanediol and toluene diisocyanate (primarily 2,4-toluene diisocyanate.) The cured resin had a hardness of Shore A 46.

The coating material is applied to the pin core as an uncured liquid mixture of resin ingredients and is thereafter cured for a time and temperature suicient to solidify the resin mixture, e.g. for the above specific composition: tor about 3 hours at about 285 F. The bowling pin core and coating was then turned to a size slightly smaller than the regulation bowling pin size and outer protective coating 16 was applied to bring the pin up to regulation size. Coating 16 may advantageously be omitted, e.g., where coating 15 gives proper dirt resistance and coeflicient of friction.

For comparison purposes, there is illustrated in FIG- URE 2 another bowling pin 20 having a head portion 21, a neck portion 22, and a shoulder portion 23 and including a core 24, a resilient elastomeric coating 25 and an outer more tenacious coating 26. Core 24 is of a normal core conguration with the core generally following the outer pin surface contour in the neck and shoulder regions. It will be readily apparent from a comparison of the pins of the two figures that core 14 has its minimum diameter extended somewhat below the minimum diameter of the pin 10 in the neck region while the minimum ldiameter of core 24 coincides substantially with the minimum neck diameter of pin 20.

' the normal core conguration.

`The lower extension of the sm-aller core diameter from fthe neck, eig., into the shoulder region of the pin as illustrated in FIGURE 1, appreciably affects the natural freque'ncy of the pin when struck by a bowling ball. 'The .transition of `stiffness in core 14 from the neck into `the shoulder region is significantly more gradual than in Normally, the head and neck of a bowling pin are the predominant resonating members producing audible sound. It is known that if stiffness of a member increases, its natural frequency increases and if stiffness decreases, natural frequency decreases. As the length of the member increases, its stiffness decreases, and, therefore, its natural frequency also decreases. Since the core stiffness in the illustrated bowling pin, and, therefore, its cross sectional area moment of inertia, is greater than that of the coating, the core is the major contributo-r of natural frequency to the pin, the coating producing a dampening effect. The lack of contribution of the coating toward natural frequency and its dampening effect can be better understood when it is considered that a bowling pin of regulation size consisting entirely of sound, hard maple will vibrate at a frequency of about 1200, e.g., 1200 to 1250, cycles per second when struck by a bowling ball while a maple plastic-coated bowling pin will vibrate at a lfrequency of about 1050 cycles .per second.

It is known that stiffness or area moment of inertia may be varied by varying other physical characteristics of an elongate hollow member, e.g., by varying wall thickness, diameter and/or section modulus, among others.

By extending the length of the major vibrating member of the bowling pin, i.e., the head and neck portion of the core, to a lower effective point in the pin, the natural frequency and especially predominant audible vibration of the pin may be accordingly decreased. Thus, depending upon the amount of extension of the length of the major audible vibrating member, the bowling pin can, in effect, be tuned. This is an advantageous aspect of the present invention in that a pin made of metal or other material which normally has a higher natural frequency, can be tuned to a frequency close to that of a plasticcoated wood pin, eig., to a frequency in the range of 1050 to 1300 cycles per second or preferably 1200 to 1250 cycles per second, or to any other desired frequency so that the difference in resonance would be less noticeable to a bowler or for other purposes.

The lengthening of the major vibrating member producing audible sound in the pins of the present invention moves the effective core vibration point lower into the bowling pin. Because the stiffness or area moment of inertia varies approximately with the third power of the diameter (the fourth power assuming a hollow core with the inner `diameter held constant), as the outer diameter of the core increases, the area moment `of inertia also increases. An increase in area moment of inertia results in -decrease in natural frequency and thus would define the approximate position' from which the upper portion of the core vibrates, assuming uniform thickness of the core member. However, in the embodiment of FIGURE 1, the core thickness is decreased below the neck as the core dia-meter begins to increase in the shoulder portion. The decrease in thickness is sufficient to keep the area moment of inertia of the core from increasing materially until beyond the initial increase in diameter. This further lowers the effective vibration point of core 14, and, therefore, further adds to the length and detracts from the stiffness of the vibrating portion for resulting decreased natural frequency.

It will also be noted by comparison of FIGURES 1 and 2 that a smaller diameter of core is also provided in the head section in the embodiment of this invention as shown in FIGURE 1. Although this smaller d-iameter does not materially affect the vibration point, it permits the use of additional weight in the form of a thicker coating of dampening material 15 in the head region of the pin, thereby further dampening the pin sound. The resulting added mass also serves to decrease natural frequency. Thus, in accordance herewith, the lowering of the minimum area moment of inertia of the core in the pin, either by extending the smaller core diameter as described above or by providing less core thickness as the diameter enlarges or both, may be used to tune a bowling pin vor may be combined with the use of applied weight in the head of the pin, eg., by increased coating thickness, for tuning purposes.

With reference to FIGURE 1, in the exemplary embodiment shown there -is provided a top closure or plug 17 in opening 18 of hollow core 14. Plug 17, which is preferably centrally or coaxially disposed with respect to the core, closes the pin top and also functions to further control pin sound. Plug 17 or portion 17a thereof is preferably of a material which is dissimilar from the material of core 14 to provide a sound dampen- .ing effect. Also, it is preferred to include a rigid vi=brating member such as coaxially or centrally disposed metal cylinder 17b within the resilient material for vibration therein to effect further dampening of sound. The mass of the vibrating member may also serve to decrease natural `frequency in the pin.

Also in the exemplary embodiment of FIGURE l there is additional provision for sound dampening in the form of an annular mass of core metal indicated at 19, adding more we-ight at the top of the pin for additional frequency control. Portion 19 of the core, as well as plug 17 including vibrator 17b, also serves to balance the Ipin with respect to weight, raising the center of gravity more closely to that of a plastic coated maple pin.

We claim:

1.- A bowling pin having a closed top and comprising a one-piece integral vibrating hollow core extending from the head region through the neck and shoulder regions and into the belly region of the pin, and a coating on the core, said core including a large diameter core portion in the belly region, a smaller diameter core portion at the minimum diameter of the pin in the neck region, said core extending from the neck core portion at a generally constant diameter into the shoulder portion of the pin, merging with the belly portion of the core through an outwardly extending core portion having a wall thickness less than the wall thickness of said core in said neck region and changing the frequency of flexural mode vibration of the head and neck relative to the belly of the pin to provide adjusted sound characteristics to the pin such that the pin has a predominant, audible, natural frequency in the range of the predominant, audible, natural frequency of a plastic-coated, hard core, maple pin.

2. A bowling pin having a closed top and comprising a one-piece integral vibrating core extending from the head region through the neck and shoulder regions and into the belly region of the pin, and a coating on the core, said core including a large diameter core portion in the belly region, a smaller diameter core portion at the minimum diameter of the pin in the neck region, said core extending from the neck core portion at a generally constant diameter into the shoulder portion of the pin and changing the frequency of flexural mode vibration of the head and neck relative to the belly of the pin to provide adjusted sound characteristics to the pin such that the pin has a predominant, audible, natural frequency in the range of the predominant, audible, natural frequency of a plastic-coated, hard core, maple pin, and an outwardly extending core portion merging the smaller diameter core portion with the large diameter belly porttion of the core.

3. A bowling pin comprising a one-piece integral vibrating hollow core extending from the head region through the neck and shoulder regions and into the belly region of the pin, and a coating over the core, said core including a large diameter core portion in the belly region, a smaller diameter core portion at the minimum diameter of the pin in the neck region, and an outwardly extending core portion of an increasing diameter merging the smaller diameter core portion with the large diameter belly core portion, said outwardly extending core portion having a wall thickness less than the Wall thickness of said neck region core portion and changing the frequency of flexural mode vibration of the head and neck relative to the belly of the pin to provi-de adjusted sound characteristics to the pin such that the pin has a predominant, audible, natural frequency in the range of the predominant, audible, natural frequency of a plasticcoated, hard core maple pin.

References Cited by the Examiner UNITED STATES PATENTS 1,060,932 5/1913 Mussey 273-82 1,491,279 4/ 1924 Stewart 273-82 2,775,456 12/1956 Schroeder et al. 273-82 2,944,821 7/1960 Mason 273-82 3,044,777 7/ 1962 Friedman 273-82 3,048,400 8/ 1962 Friedman 273-82 DELBERT B. LOWE, Primary Examiner.

RICHARD C. PINKHAM, Examiner. 

1. A BOWLING PIN HAVING A CLOSED TOP AND COMPRISING A ONE-PIECE INTEGRAL VIBRATING HOLLOW CORE EXTENDING FROM THE HEAD REGION THROUGH THE NECK AND SHOULDER REGIONS AND INTO THE BELLY REGION OF THE PIN, AND COATING ON THE CORE, SAID CORE INCLUDING A LARGE DIAMETER CORE PORTION IN THE BELLY REGION, A SMALLER DIAMETER CORE PORTION AT THE MINIMUM DIAMETER OF THE PIN IN THE NECK REGION, SAID CORE EXTENDING FROM THE NECK CORE PORTION OF THE PIN, CONSTANT DIAMETER INTO THE SHOULDER PORTION OF THE PIN MERGING WITH THE BELLY PORTION OF THE CORE THROUGH AN OUTWARDLY EXTENDING CORE PORTION HAVING A WALL THICKNESS LESS THAN THE WALL THICKNESS OF SAID CORE IN SAID NECK REGION AND CHANGING THE FREQUENCY OF FLEXURAL MODE VIBRATION OF THE HEAD AND NECK RELATIVE TO THE BELLY OF THE PIN TO PROVIDE ADJUSTED SOUND CHARACTERISTICS TO THE PIN SUCH THAT THE PIN HAS A PREDOMINANT, AUDIBLE, NATURAL FREQUENCY IN THE RANGE OF THE PREDOMINANT, AUDIBLE NATURAL FREQUENCY OF A PLASTIC-COATED, HARD CORE, MAPLE PIN. 